Medical treatment of various illnesses or diseases commonly includes the use of one or more medical devices. Two types of medical devices that are commonly used to repair various types of body passageways are an expandable graft or stent, or a surgical graft. These devices have been implanted in various areas of the mammalian anatomy. One purpose of a stent is to open a blocked or partially blocked body passageway. When a stent is used in a blood vessel, the stent is used to open the occluded vessel to achieve improved blood flow which is necessary to provide for the anatomical function of an organ. The procedure of opening a blocked or partially blocked body passageway commonly includes the use of one or more stents in combination with other medical devices such as, but not limited to, an introducer sheath, a guiding catheter, a guide wire, an angioplasty balloon, etc.
Various physical attributes of a stent can contribute directly to the success rate of the device. These physical attributes include radiopacity, hoop strength, radial force, thickness of the metal, dimensions of the metal and the like. Cobalt and chromium alloys and stainless steel are commonly used to form stents. These materials are commonly used since such materials having a known history of safety, effectiveness and biocompatibility. These materials how ever have limited physical performance characteristics as to size, strength, weight, bendability, biostability and radiopacity.
The materials commonly used to form prior stents are biostable materials that remained in the blood vessel long after the stent had achieved its function. As such, the continued presence of the stent in the blood vessel increased the risks associated with thrombosis, in-stent restenosis, vascular narrowing and/or restenosis in the blood vessel at the location of the stent. The presence of the stent in the blood vessel also created a potential obstruction to later medical procedures that attempted to correct problems in a body passageway upstream from the stent. The stent was also prone to fracturing over time, especially when the stent was located in regions exposed to bending (e.g., leg, arms, neck, etc.). The repeated bending of the stent could eventually fatigue the stent, thereby resulting in one or more portions of the stent fracturing and/or becoming loose from the stent. These fractures (e.g., strut fractures, etc.) and/or loose portions of the stent could result in damage to the blood vessel and/or one or more regions of the vascular system downstream of the stent.
The current invention is generally directed to a medical device that is at least partially formed of novel biodegradable or bioabsorbable polymer that enhances one or more of the physical properties of a medical device so as to improve the success rate of such medical device and to overcome several of the past problems associated with such medical devices.